The murder of Laci Peterson and her unborn son Conner still draws worldwide attention almost 15 years later. The I-Team has an exclusive interview with her mother and what she says happened the last time she saw her daughter alive that made her doubt her son-in-law, Scott Peterson. (KGO-TV)

The murder of Laci Peterson and her unborn son Conner still draws worldwide attention almost 15 years later. The ABC7 News I-Team has been able to examine more than a thousand pieces of evidence, some of which has been made public for the first time, and has an exclusive interview with Laci's mom.

Sharon Rocha says something happened the last time she saw her daughter alive that made her doubt her son-in-law, Scott Peterson. But it took hard evidence, including secretly recorded conversations, to help solve the murders of Laci and Conner and put Scott on death row.

Laci Peterson's family reported her missing on Christmas Eve 2002. She was 8 months pregnant when she disappeared from her Modesto home.

The ABC7 News I-Team obtained access to more than a thousand pieces of evidence, including photos, documents, and recordings -- some of it has never made it to the public.

"When you go into the Bay Area and you look at that ocean you think - there is a lot of water in this state," said Sharon.

Holding onto hope, Laci's family kept in close contact with Modesto detectives working the case.

"You're always suspicious of pretty much everybody," said retired Detective Jon Buehler. "I mean we weren't suspicious of Sharon, of course, because of her naked honesty and emotions. I mean, she couldn't manufacture those. You could tell that that was from the heart."

Sharon and her family had a change of heart about Scott when a story surfaced about his mistress, 30-year-old Amber Frey, a single mom.

The morning that story broke, Laci's brother, Brent Rocha, confronted Scott on a phone call. On that call you can hear Scott telling him: "I was trying to find an Enquirer but I couldn't so I don't know exactly what this article says."

That secretly recorded call was one of dozens of taped phone conversations among more than a thousand pieces of evidence the I-Team reviewed at the Modesto courthouse.

Part of the calls included:

Brent: "There's pictures of you and the girl together. So we know that's true, right"Scott: "Yeah, there was an encounter."Brent: "What can you tell me about my sister to make me understand that you're telling the truth and I that could still support you?"Scott: "You know, I don't know if you can believe me. I certainly hope you can. I hope you know me well enough."Brent: "You had nothing to do with this?"Scott: "I had nothing to do with her disappearance, Brent. I wish I knew where she was."

Laci's mother grilled Scott on the phone the same day:

Sharon: "The last night I talked to Laci, what was going on? What happened after 8:30 that night? Were you at home when she called me?"Scott: "Yeah. We watched a movie. We picked up a pizza and watched a movie and went to bed."Sharon: "What movie?"Scott: "'The Rookie.'"Sharon: "What was she wearing when she went to bed?"Scott: "My pajamas, those blue ones."Sharon: "How come she was wearing your blue pajamas?"

His said his relationship with Laci's family was strained after they learned of his affair with Amber Frey.

Diane: "What have they said to you?"Scott: "They're obviously upset with me about the romantic relationship Amber. But I believe that they're still looking for Laci and I would like to work with them."

Laci's mother says she didn't want to believe Scott was involved.

"If Laci comes home, how's she going to feel about me if I'm suspecting her husband had something to do with it," said Sharon.

"She said the baby was kicking so I put my hand on her stomach because I'd never felt him kick," said Sharon. "She leaned over to me and said, 'Mom, Scott doesn't like to do this.' She said, 'I've asked him to feel my stomach when the baby kicks and he never wants to touch my stomach.' That really really bothered me and that was the last time I saw her."

Scott Peterson was convicted of first and second degree murder. He's on death row at San Quentin.

Two previous appeals he filed seeking a new trial have been rejected, but he has filed another. He will turn 45 next month.

Laci would have turned 42 in May, and their son Conner would have been 14 years old.